The present invention relates to preparing overlay""s to verify printing plates, using a lamination method that uses pressure or heat and pressure to laminate media together.
Pre-press proofing is a procedure that is used primarily by the printing industry for creating representative images of printed material. In the printing industry, pre-press proofs are used to check for color balance, control parameters, and other important image quality requirements, without the cost and time that is required to actually produce printing plates, set up a printing press, and produce an example of an representative image, which results in higher costs and loss of profits that would ultimately be passed on to the customer.
To create a pre-press proof, first, an original image is separated into individual color separations or digital files. The original image is scanned or separated into the three subtractive primaries and black. Typically, a color scanner is used to create the color separations or digital files and in some instances more than four color separations or digital files are used. Although there are several ways used in the printing industry to create a pre-press proof from the color separations or digital files, they are generally of three types. The first method being a color overlay system that employs the representative image on a separate base for each color, then the image is overlaid on each other to create a pre-press proof. The second method uses a single integral sheet process in which the separate colors for the representative image are transferred one at a time by lamination onto a single base. The third is a digital method in which the representative image is produced directly onto a receiver stock, from digital files.
The representative image to be laminated can be, but is not limited to being created on a commercially available Kodak image processing apparatus, depicted in commonly assigned U.S. Pat. No. 5,268,708 which describes an image processing apparatus having half-tone color imaging capabilities. The above-mentioned image processing apparatus is arranged to form a representative image onto a sheet of thermal print media. In this process, dye from a sheet of dye donor material is transferred to the thermal print media by applying a sufficient amount of thermal energy to the dye donor sheet material to form the intended image. The image processing apparatus is comprised generally of a material supply assembly consisting of a lathe bed scanning subsystem. The scanning subsystem includes: a lathe bed scanning frame, translation drive, translation stage member, printhead, imaging drum, and media exit transports.
The operation of the image processing apparatus comprises: metering a length of the thermal print media (in roll form) from the material supply assembly. The thermal print media is then measured and cut into sheet form of the required length and transported to the imaging drum, registered, wrapped around, and secured onto the imaging drum. Next, a length of dye donor material (in roll form) is also metered out of the material supply assembly, then measured and cut into sheet form of the required length. It is then transported to the imaging drum and wrapped around the imaging drum utilizing a load roller which is described in detail in commonly assigned U.S. Pat. No. 5,268,708. By wrapping, it is superposed in the desired registration with respect to the thermal print media (which has already been secured to the imaging drum).
After the dye donor sheet material is secured to the periphery of the imaging drum, the scanning subsystem or write engine provides the imaging function. This imaging function is accomplished by retaining the thermal print media and the dye donor sheet material on the imaging drum while it is rotated past the printhead. The translation drive traverses the printhead and translation stage member axially along the axis of the imaging drum, in coordinated motion with the rotating imaging drum. These movements combine to produce the intended image on the thermal print media.
Once a representative image has been formed on the thermal print media, the dye donor sheet material is then removed from the imaging drum. This is accomplished without disturbing the thermal print media that is beneath it. The dye donor sheet material is then transported out of the image processing apparatus by means of the material exit transport. Additional dye donor sheet materials are sequentially superimposed with the thermal print media on the imaging drum. These materials are them imaged onto the thermal print media previously mentioned until the representative image is completed and transferred onto the thermal print media. The completed representative image formed thereon is then unloaded from the imaging drum and transported by the receiver sheet material exit transport to an exit tray in the exterior of the image processing apparatus.
After a representative image has been formed on the thermal print media as previously described, it is then transferred to a receiver stock such that the pre-press proof is representative of an image that would be printed on a printing press. A Kodak Laminator as described in U.S. Pat. No. 5,478,434 can be used to bond or laminate the representative image as part of a pre-press color proofing system but this invention is not limited to the use of this device. U.S. Pat. No. 5,203,942 describes a Kodak Laminator that employs a lamination/de-lamination system as applied to a drum laminator, and pending U.S. patent application Ser. No. 09/676,877 describes a Kodak Laminator that employs endless belts incorporated into the lamination apparatus. For the purpose of this patent application the laminator described in pending U.S. patent application Ser. No. 09/676,877 will be used. It should be noted that the present invention described in this disclosure is not limited to a Kodak Laminator or to the type of laminator reference above.
Generally laminating a pre-press proof is a two pass process. For the first step, a sheet of pre-laminate, which has a pre-laminate support layer and a thermal print layer, encapsulation or protective layer, is placed on top of a receiver sheet, which is also called xe2x80x9creceiver stockxe2x80x9d in the industry. This construction of multiple layers is a lamination sandwich, which is fed into the laminator. Once the lamination sandwich exits the laminator the pre-laminate support layer is peeled away from the now pre-laminated receiver stock.
For the second pass, the imaged thermal print media with the representative image formed thereon is placed on the pre-laminated receiver stock with representative image face down on the pre-laminated receiver stock and fed into the laminator. After the lamination sandwich has exited the laminator, the thermal print support layer is peeled away, leaving the completed pre-press proof simulating an image produced on a printing press.
While the above-described lamination method works well for both laser thermal inkjet pre-press proofs, there exists a need for an overlay to verify the image on printing plates prior to being used on the printing press.
The present invention provides a method of forming overlays to verify a printing plate. The novel methods of the present invention are preferably for forming an overlay to verify a printing plate, but not limited to with a resolution of between about 1400 and 4000 dpi and most preferably having a resolution of about 1800 to 3000 dpi. The imaged receiver sheet can have a monochrome image or multicolor image. The support layers can comprise a release layer, an aluminized layer, and a support base or combination thereof, or just a support base. The base can be made from polyester, polyethylene, or other materials well known in the art. The thermal print layers have a thickness ranging from 1 micron to 75 microns, and more preferably from 1 to 25 microns.
The invention also relates to a method for verifying an image on a printing plate comprising the steps of: an overlay forming the method consisting of: creating an imaged receiver sheet having an image, a first thermal print layer, and a support layer; laminating an imageless receiver sheet having a second thermal print layer and a second support layer, which is preferably clear with the imaged receiver sheet, thereby encapsulating the image between the first thermal print layer and the second thermal print layer; removing the first support layer; removing the second support layer; adhering an overlay to a printing plate having an image, using an electrostatic charge; and viewing the overlay against the image on the printing plate for image quality and content.
The invention also relates to a method for verifying the image on a printing plate comprising the steps of: forming an overlay by the method consisting of: creating an imaged receiver sheet having an image, a first thermal print layer, and a first support layer; laminating an imageless receiver sheet having a second thermal print layer and a second support layer with the imaged receiver sheet thereby encapsulating the image; removing the first support layer; and adhering an overlay to a printing plate having an image, using an electrostatic charge.
The invention, its objects and advantages, will become more apparent in the detailed description of the preferred embodiments presented below.